Ether-containing dibasic fatty acid metal soap thickened greases

ABSTRACT

Monohydroxy fatty acids or esters are cyanoethylated and the cyanoethoxy fatty derivative is treated with dilute hydrogen peroxide in a weakly basic medium to convert the cyano group to an amide function which is then hydrolyzed to the dibasic acid. The dibasic acid is reacted with an appropriate metallic base such as lithium, sodium and calcium to make the dibasic soap which is dispersed in a petroleum oil base or a synthetic base oil of the diester type to form a grease.

United States Patent Kenney et al.

ETHER-CONTAINING DIBASIC FATTY ACID METAL SOAP THICKENED GREASES Inventors: Harold E. Kenney, Jenkintown;

Edward T. Donahue, Philadelphia, both of Pa.

The United States of America as represented by the Secretary of Agriculture, Washington, DC,

Filed: Aug. 24, 1973 Appl. No.: 391,182

Related US. Application Data Division of Ser. No, 275,009, July 25, 1972,

Assignee:

US. Cl 252/39, 252/41, 252/400 Int. Cl..... C10m 5/16, ClOm 5/14, ClOm 7/24 Field of Search 252/39, 41, 400

References Cited UNITED STATES PATENTS 9/1958 Andress 252/39 ll/l962 lO/l966 Pethrick et al. 252/4l Morway et al 252/4] Primary Examiner-Daniel E. Wyman Assistant Examinerl. Vaughn Attorney, Agent, or Firm-M. Howard Silverstein; Max D. Hensley; William E Scott [57] ABSTRACT Monohydroxy fatty acids or esters are cyanoethylated and the cyanoethoxy fatty derivative is treated with dilute hydrogen peroxide in a weakly basic medium to convert the cyano group to an amide function which is then hydrolyzed to the dibasic acid. The dibasic acid is reacted with an appropriate metallic base such as lithium, sodium and calcium to make the dibasic soap which is dispersed in a petroleum oil base or a synthetic base oil of the diester type to form a grease.

9 Claims, N0 Drawings ENTER-CONTAINING DIBASIC FATTY ACID METAL SOAP THICKENED GREASES This is a division of application Ser. No. 275,009 filed July 25, 1972.

A non-exclusive, irrevocable, royalty-free license in 5 the invention herein described. throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to metallic dibasic fatty soaps and more specifically to the use of such soaps to make multi-purpose greases.

The addition of chemical compounds to lubricants is not new. In fact, certain chemical compounds are commonly added in small amounts to lubricants to improve their physical properties. Typical additives include oxidation or corrosion inhibitors. wear improvers, water repellants and dyes. One problem in a formulated grease containing additives is that in storage and in use these additives tend to migrate in the base oil and in extreme cases cause the grease to separate. Another problem is the frequent tendency for two additives to be incompatible. This often complicates the task of formulation.

The soaps of this invention improve the thermal stability and wear properties of the base oils with which they are mixed and thus decrease the need for additives to improve these properties. Another important aspect of this invention is that since the thermal stability, wear and grease forming properties are embodied in one molecule, it is impossible for migration or incompatibility to occur in the resulting grease.

ln addition to being grease formers, the fatty derivatives of this invention impart thermal stability and antiwear properties to the resulting greases. These derivatives also form greases with less than half the amount of soap normally used and they have the added feature of forming two classes of greases from two types of base oils; that is, diester type oils such as di(2-ethylhexyl) sebacate (DOS) and petroleum oils such as l00 paraffin oil.

One object of this invention is to prepare stable greases by dispersing difunctional soaps in petroleum oil of lubricating viscosity.

Another object is to prepare stable greases by dispersing difunctional soaps in synthetic base oils of the diester type.

Still another object is to provide difunctional fatty soap derivatives that impart thermal stability and antiwear properties to greases.

In general, according to this invention the above objects are accomplished by dispersing in petroleum oil or in a synthetic base oil of the diester type, a dibasic fatty soap of the general formula:

wherein the sum ofx and y is a number from 10 to l9 and R is a metallic ion capable of forming a fatty soap such as Na", Li and Caf. As seen in the formula above, these fatty derivatives are novel compounds in which a 3 carbon side chain having a terminal carboxyl group is attached by an ether linkage to the carbon chain of the fatty soap.

Suitable starting materials for the greases formed in this invention are monohydroxy fatty acids or their ester derivatives either naturally occurring or synthesized by suitable known procedures. The monhydroxy fatty compounds are cyanoethylated by the method of copending application, Ser. No. 852,469 now U.S. Pat. No. 3,70l,802 filed Aug. 22, I969, by dissolving them in acrylonitrile and adding a strong base to catalyze the reaction. The cyanoethoxy fatty derivative is then treated with dilute hydrogen peroxide in weakly basic medium. This treatment converts the cyano group to an amide function which isthen hydrolyzed to the dibasic acid by refluxing with aqueous HCl. The resulting dibasic acid is then caused to react with the desired base, and the dibasic soap is isolated. The grease can be made by adding the appropriate amount of dibasic soap (7-20 percent) to the base oil. lfa synthetic diester oil such as di-(2-ethylhexyl) sebacate (D.O.S.) is used, the oil is heated to between 200-220C and the soap added slowly with stirring. On cooling a stable grease forms. If a petroleum base oil is used, it is heated to ll75C and the dibasic soap added, and the mixture cooled slowly with stirring to form a grease.

The greases formed from dibasic fatty soaps and diester oils have good thermal stability and in the case of the disodium soap, exceptional good thermal properties. The anti-wear properties are also considerably better than a grease formulated from sodium stearate and a diester oil. The greases formed from the dibasic fatty soaps and petroleum oils also have better thermal stability and anti-wear properties than the grease formed from sodium stearate and a petroleum oil.

In the preparation of the cyanoethoxy fatty grease precursor, suitable monohydroxy fatty acids may vary in chain length from l0-20 carbon atoms. and the hydroxy group may be attached at any point on the chainv The cationic portions of the soap may be chosen from any of the elements commonly used in manufacturing soaps. For the purposes of this invention we have used lithium, sodium and calcium.

The greases formed from diester fluids can be formulated using any of the diester oils such as di-(2- ethylhexyl) sebacate (D.O.S.). Suitable oils for the petroleum based greases may be any hydrocarbon oil of lubricating viscosity such as I00 paraffin oil.

The amount of dibasic soap used in this invention to form greases is less than 20 percent by weight of form ulated grease. The greater the amount of soap used the harder the grease. In this invention, stable greases were made using 7-20 percent soap. The thermal and wear properties as measured by dropping point and four ball wear tester are improved at the higher percentages of soap.

in the preparation of the metal salts of these dibasic acids, it has been necessary to interpose the amide in the hydrolysis of the cyano function to the acid. Direct hydrolysis has been found practical [JA'OCS 46, 1-4 (1969)]. The dibasic acids themselves, of course, are new and not found in the prior art.

The thermal stability properites of the greases described in this patent were determined using the dropping point method (A.S.T.M. D-566). This procedure measures the temperature at which the grease passes from a semisolid to a liquid state and is a qualitative indication of the heat resistance of the grease.

Anti-wear properties were determined using the Shell Four Ball Wear Tester as described by A.S.T.M. desig nation D2266-64T. Federal test method standard No. 79l6. Approximately ml of the grease to be tested is placed in the test cup so that the three bottom stationary balls are covered. After positioning the cup on its stand in contact with the fourth ball the grease was heated to 75C. a kg load was placed on the weight tray. and the upper ball was allowed to rotate at l200 rpm. for 1 hour. The diameters of the scars worn on the three stationary balls were measured by means of a low power microscope. The results are shown in Table l. The hardness of the greases was determined with a Penetrometer as described by A.S.T.M. designation D2l748. A micro-cone was used to check the consistency of small samples. Some of the physical properties of the greases are shown in Table l.

The invention is exemplified as follows:

Fifty grams (0.16 moles) of methyl l2- hydroxystearate was dissolved in 500 ml. (75 moles) of acrylonitrile containing 2.5 ml. water. To this mixture was added. rapidly with stirring, l0 ml. of a 40 percent aqueous solution of benzyltrimethylammonium hydroxide. Polymerization of the excess acrylonitrile occurred at four minutes. Fifty ml. of water containing 3 ml. HCl was added at this point. The resulting mixture was extracted with three 300 ml. portions of ether. The combined extracts were washed with water. dried over sodium sulfate and evaporated to a residue weight of 55.9 g. gas liquid chromatography (G.L.C.) analysis confirmed that the residue was predominately methyl l2(2-cyanoethoxy) stearate. Recrystallization from hexane gave a 97+ percent pure product. To a stirred solution of g. (0.l4 moles) of methyl l2(2- cyanoethoxy) stearate in 150 ml. ethanol at 0C. was added slowly a precooled (10C.) mixture of 500ml. 7 percent aqueous hydrogen peroxide and 250 ml. 95 percent ethanol. The reaction mixture was adjusted to pH 10 by addition of dilute aqueous sodium hydroxide solution and stirred at C for 3 hours and then cooled to room temperature. The mixture was acidified with dilute HCl and extracted with three 500 ml. protions of ether. The combined extracts were washed with water, dried over anhydrous sodium sulfate and evaporated to a residual weight of 5l g. The infrared (l.R.) spectrum of the residue showed the cyano function was converted to amide. A solution of 51g (014 moles) of this amide derivative in one liter of 30 percent aqueous HCl was allowed to reflux for 2 hours. then cooled to room temperature and extracted with three 300 ml portions of ether. The combined extracts were washed with water. dried over sodium sulfate, and evaporated to a solid white residue. (52g) Thin layer chromatagraphy (T.L.C.) and [.R. analysis indicated an essentially pure compound having strong bonds at 1705 cm (acid C=O), 1 I00 cm (COC). A recrystallized sample had a melting point of 6364C. Elemental analysis showed the compound to be l2(2-carboxyethoxy)- stearic acid. From this diacid the following soaps were prepared:

62g (017 moles) of the above diacid was dissolved in 250 ml acetone and l4.lg (0.35 moles) lithium hydroxide in 100 ml water was added to it with stirring. After stirring for l hour, 500 ml acetone was added and the mixture filtered and the soap dried under vacuum at l l0C to give 58g of a white powder; melting point ll75; lithium content 4.08 percent.

Using the procedure described above, the disodium soap; m.p. 2l2l25, sodium content 129 percent, and the dicalcium soap; m.p. l86-l88, calcium content 9.58 percent were prepared.

PREPARATION OF DlESTER TYPE GREASE l.5g ofthe disodium soap was added slowly with stir ring to 8.5g di-(Z-ethylhexyl) sebacate at 220C. After heating and stirring for 0.5 hours the mixture was allowed to slowly cool with stirring. The resulting product was a stable yellow grease.

Using the procedure described above the dilithium and dicalcium soap diester greases were prepared. PREPARATION OF PETROLEUM TYPE GREASE 1.0 g. of the disodium soap was added slowly with stirring to 9.0 g. of 100 paraffin oil at lC. After stir ring at l70C for 0.5 hours, the mixture was allowed to cool. The resulting product was a dark brown grease.

Using the procedure described above the dilithium and dicalcium soap I00 paraffin oil greases were pre pared.

TABLE I NCLl Dropping Wear scar Bast. .i Grade Point din. Soap Oil Soap Hard- F mm.

disodium D.O.S Ill 4 500+ 0.643 do. l5 3 500+ 0.686 do. ll] l 332 0.7M) dilithium DO 8. 20 t 402 llblit do [5 2 378 (l 645 do If] I 345 l) 699 do. 7 0 297 0.747 dicalcium D08. 20 5 T ll 0 755 do l5 3 274 0790 do. ll] 0 0.820 disodium I00 Paraffin l5 2 407 0 523 Oil do III I 340 0.56. dilithium IOU Paraffin If] i) 35] 0.596

Oil dicalcium I00 Paraffin l5 2 A 0.54l

Oil do. If] I 0.580

We claim:

1. A multipurpose grease comprising a major amount of a lubricating oil selected from the group consisting wherein the sum of .r and y is a number from 10 to 19 and R is a metallic ion capable of forming a fatty soap.

2. The grease of claim 1 wherein the lubricating oil is paraffin oil.

3. The grease of claim 2 wherein the sum of .t and y in the dibasic fatty soap is 15 and the metallic ion is lithium.

4. The grease of claim 2 wherein the sum of .r and y in the dibasic fatty soap is 15 and the metallic ion is so dium.

5. The grease of claim 2 wherein the sum of .r and y 5 6 in the dibasic fatty soap is 15 and the metallic ion is cal- 8. The grease of claim 6 wherein the sum of x and y cium. in the dibasic fatty soap is 15 and the metallic ion is 6. The grease of claim 1 wherein the lubricating oil dium. is di-(2-ethylhexyl sebacate. 9. The grease of claim 6 wherein the sum ofx and y 7. The grease of claim 6 wherein the sum of x and y in the dibasic fatty soap is and the metallic ion is calin the dibasic fatty soap is 15 and the metallic ion is cium. lithium. 

1. A MULTIPURPOSE GREASE COMPRISING A MAJOR AMOUNT OF A LUBRICATING OIL SELECTED FROM THE GROUP CONSISTING OF PARAFFIN OIL AND ALIPHATIC DIESTER OIL AND A MINOR THICKENING AMOUNT OF A DIBASIC FATTY SOAP OF THE FORMULA
 2. The grease of claim 1 wherein the lubricating oil is paraffin oil.
 3. The grease of claim 2 wherein the sum of x and y in the dibasic fatty soap is 15 and the metallic ion is lithium.
 4. The grease of claim 2 wherein the sum of x and y in the dibasic fatty soap is 15 and the metallic ion is sodium.
 5. The grease of claim 2 wherein the sum of x and y in the dibasic fatty soap is 15 and the metallic ion is calcium.
 6. The grease of claim 1 wherein the lubricating oil is di-(2-ethylhexyl sebacate.
 7. The grease of claim 6 wherein the sum of x and y in the dibasic fatty soap is 15 and the metallic ion is lithium.
 8. The grease of claim 6 wherein the sum of x and y in the dibasic fatty soap is 15 and the metallic ion is sodium.
 9. The grease of claim 6 wherein the sum of x and y in the dibasic fatty soap is 15 and the metallic ion is calcium. 